pete@octopus.UUCP (Pete Holzmann) (05/15/88)
In article <1596@gumby.cs.wisc.edu> g-thaler@gumby.cs.wisc.edu (Maurice Thaler) writes: }I have recently ordered and am waiting for an ARLL card from Perstor }out of Scottsdale AZ....[one version has] }RAM on the card to perform }caching to improve the data transfer rate. According to the stats from }CORETEST2.7 my hard disk (ST 4096 80Megabyte) gets about 250k/sec with a }standard WD control card. The tech at Perstor said that in my 386, I can }expect to get a transfer rate close to 2000k/sec with this new card and }the size will be 1.9x or aprox 150 meg. 1.9 times the storage capacity is a reasonable claim. 2000K/sec is crazy. I suppose if you call the transfer rate from cache memory a 'transfer rate', this claim would be ok; but a P.D. disk cache program running in regular (or Extended/EMS) memory would do just as well. A 1:1 ARLL controller that provides 1.9 times the storage capacity will give you 1.9 times the transfer rate of a 1:1 MFM controller! (See my article on RLL details for why). This works out to: 60 (rotations/sec) * 17 (sec/track in MFM) * .5K (bytes/sec in MFM) * 1.9 (ARLL vs MFM) = 969K/sec. This is slower, for example, than an ordinary ESDI drive. [Hmmmm. I just checked: 1.9 times normal capacity indicates 'ERLL' rather than 'ARLL', not that it matters...] }He said that many RLL cards apply data at a higher frequency (I might be }misquoting him a little) on both the pre-comp and the actual data tracks, but }Perstor used a different technique which does not use the higher frequency on }the data tracks and is generally as gentle to your drive as a WD control card. That is an exaggeration in the following sense: None of the RLL drives store data at a higher frequency on the drive; they are all gentle on your drive. It is the TIMING (i.e. accuracy of placement, not density of placement) that is more stringent on any 'RLL' controller. }I am not into advertising for Perstor, but I do like the idea of inovation and }this product seemed interesting to me. I do a lot of desktop publishing and }need all the space I can get (I have almost 30 Meg of soft fonts!) as do most }other heavy computer users I know. This will not give the performance of an }ESDI drive since the access time is not increased, but a high data transfer ^^^^ you can have slow-seek ESDI, just as you can have fast-seek MFM/RLL drives! }The price of a 4096 w/ this card gives }150Meg at about half the price of the ESDI equivalent. You can't fight the 28ms }access time, but the high data transfer rate is appealing. The bottom line is what counts, and this sounds good! It'll be interesting to hear whether this controller works well with various drives. If an ERLL controller works well on a particular type of drive, we can be *certain* that normal RLL will work without any problem at all! Pete -- OOO __| ___ Peter Holzmann, Octopus Enterprises OOOOOOO___/ _______ USPS: 19611 La Mar Court, Cupertino, CA 95014 OOOOO \___/ UUCP: {hpda,pyramid}!octopus!pete ___| \_____ Phone: 408/996-7746
jeff@drexel.UUCP (Jeff White) (05/16/88)
In article <220@octopus.UUCP>, pete@octopus.UUCP (Pete Holzmann) writes: > In article <1596@gumby.cs.wisc.edu> g-thaler@gumby.cs.wisc.edu (Maurice Thaler) writes: > }I have recently ordered and am waiting for an ARLL card from Perstor > }out of Scottsdale AZ....[one version has] >. >. >. > The bottom line is what counts, and this sounds good! It'll be interesting to > hear whether this controller works well with various drives. If an ERLL I too would also be very interested in hearing what type of performance you get with the controller. Will the board be used under DOS or Xenix? The original article doesn't seem to mention it. Jeff White Drexel University - ECE Dept. rutgers!bpa!drexel!jeff
samc@hpccc.HP.COM (Samuel Chau) (05/18/88)
I have been testing the Perstor PS180 ERLL card with various drives for several months now. Whether this card will work with a particular drive depends heavily on the timing margins available, especially at the innermost cylinders. Of the three Seagate ST-251-1 drives I had played with, only two worked smoothly. The third one had significantly lower margin figures listed in the accompanying tech sheet. The last 200 cylinders of that drive were unable to hold valid data. Over half of the clustors in that region were spared by the high-level format program. And I chose not to trust any data to any of the surviving clustors. To be safe, when purchasing a drive for use with the Perstor PS180, one would almost need to ask for several drives of the same make and model to be displayed at once. Then the one with the highest margin figures listed (on the tech sheet) would be the best choice. The number of hard errors is only of secondary concern, since the drive that I now use with the PS180 has 9 hard errors, whereas the one that failed has 0 hard errors. Older drives can be expected to fail rather miserably with the PS180. I have tried two Fujitsu M2243AS 72MB mechanisms made two years apart without a bit of luck with either drive. I would think RLL qualified drives should have the best chance of working with a demanding controller like the PS180, but they may not provide the most cost effective means of getting more disk space. I, too, would like to hear from others who have had experience with the Perstor PS180 card. ***************************************************************** * DISCLAIMER * * The opinions expressed above are strictly my own, not those * * of Hewlett Packard Company. * ***************************************************************** Sam Chau HP Cupertino ...hplabs!hpccc!samc (408) 447-0238